Heretofore efforts have been made to utilize by a heat exchanger some of the heat remaining in the exhaust gases after it leaves the furnace and before entering the exhaust stack. Examples of such heat exchanger are shown in the following U.S. Pat. Nos.:
2,468,909 PA1 3,120,225 PA1 3,944,136 PA1 350,452 PA1 2,276,400 PA1 2,362,940 PA1 3,884,292
Each of the aforementioned Patents are directed to involved complicated structures which in one way or another seek to utilize some of the exhaust heat of a furnace before it enters the stack. The above examples of efforts to utilize exhaust heat have been inefficient and include one or more of the following elements; namely, a heat exchanger to receive exhaust gases from the furnace before entering the stack; devices for transferring fresh air through the heat exchanger to utilize some of this exhaust heat, and in some cases, a source of outside fresh air for direction into the combustion chamber.